high resolution fir and ir spectroscopy of methanol isotopologues
DESCRIPTION
High Resolution FIR and IR Spectroscopy of Methanol Isotopologues. R.M. Lees, Li-Hong Xu Centre for Laser, Atomic and Molecular Sciences (CLAMS) Department of Physics, University of New Brunswick D.R.T. Appadoo, B. Billinghurst Canadian Light Source, University of Saskatchewan. - PowerPoint PPT PresentationTRANSCRIPT
High Resolution FIR and IR Spectroscopy of
Methanol Isotopologues
R.M. Lees, Li-Hong XuCentre for Laser, Atomic and Molecular Sciences (CLAMS)
Department of Physics, University of New Brunswick
D.R.T. Appadoo, B. BillinghurstCanadian Light Source, University of Saskatchewan
May 14 – Launch of Herschel Space Observatory with HIFI - Heterodyne Instrument for the Far-Infrared
• Herschel reached L2 Lagrange point in mid-July• HIFI was switched off on Aug 3 – anomaly!
Herschel PACS View of Galaxy M51 – June 14
Background and Motivation
The Herschel Space Observatory with the HIFI THz spectrometer on board was launched on May 14 and ALMA is coming – extensive methanol astronomical spectra are imminent and new lab data and insights are needed for all of the isotopic species of this principal "interstellar weed" to construct extensive databases and permit reliable modelling for astrophysical conditions.
The large-amplitude internal rotation in CH3OH makes the torsion-
vibration energy manifold both complex and interesting, with strong torsion-mediated interactions coupling the different vibrational modes and several unassigned families of substates.
By looking at the isotopologues in detail, we hope for a new VISTA into the vibrational structure [Vibrational Isotopic Shift Technique for Assignment] with further clues to the vibrational identification.
Methanol 1-D Large-Amplitude Torsion
O
H
H
H
13C
H
100
150
200
250
300
350
400
450
0 2 4 6 8 10 12K values
Etor = F<P2> + V3/2 <1-
cos3>
V3 12=1
12=00E0A
12=2
The torsional energies follow oscillating curves as a function of rotational quantum number K, with A and E torsional symmetry.
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Torsional-K-Rotational Energy Structure for CH3OH
V3= 373.59 cm-1
AE1
E2
t= 0
t= 1
t= 2
t= 3
(0,15)/(1,13)/(2,11)A
(1,10)/(2,7)A
(0,12)/(1,9)E
(0,9)/(1,5)A
(t,K)TS
Level crossings
K Values
t
Lowest SmallAmplitudeVibrations
rQ[(2,5)-(0,4)E]rQ[(3,-10)-(1,-9)E] rR[(2,14)-(0,13)E]
(vt, K)
pP[(2,2)-(0,3)A-]rR[(2,13)-(1,12)A]rR[(3,11)-(2,10)E]
FIR Spectrum of CH3OH - New High Torsional Assignments
660.5 660.6 660.7 660.8 660.9 661.0 661.1 661.2 661.3 661.4 661.5 661.6 661.7 661.8 661.9 662.0 660.5 660.6 660.7 660.8 660.9 661.0 661.1 661.2 661.3 661.4 661.5 661.6 661.7 661.8 661.9 662.0
662.0 662.1 662.2 662.3 662.4 662.5 662.6 662.7 662.8 662.9 663.0 663.1 663.2 663.3 663.4 663.5 662.0 662.1 662.2 662.3 662.4 662.5 662.6 662.7 662.8 662.9 663.0 663.1 663.2 663.3 663.4 663.5
663.5 663.6 663.7 663.8 663.9 664.0 664.1 664.2 664.3 664.4 664.5 664.6 664.7 664.8 664.9 665.0 663.5 663.6 663.7 663.8 663.9 664.0 664.1 664.2 664.3 664.4 664.5 664.6 664.7 664.8 664.9 665.0
74-62 A14-23 A
34-22 A
142-130 E2
FIR Spectrum of CH3OH – Loomis-Wood Approach
64-52 E1 24-12 E1103-92 E1
93-101 E2
113-120 E1???
vt' vt" K' K" TS obs / cm-1 Olap El vt' vt" K' K" TS obs / cm-1 Olap El
2 0 11 10 A 420.03 0.0381 3 1 11 10 E2 584.87 -0.0520 2 0 13 12 E2 499.16 0.0951 3 1 12 11 E1 530.81 -0.0627 2 0 14 13 E1 473.62 0.1070 3 1 12 11 A 620.41 0.0113 2 0 15 14 A 454.48 0.1059 3 1 13 12 A 477.58 -0.0727 2 1 12 11 E1 436.58 -0.0527 3 2 9 8 E2 600.64 -0.0220 2 1 13 12 A 470.18 -0.0590 3 2 10 9 E2 414.62 -0.0197 3 0 10 11 E2 644.93 0.0283 3 2 10 9 E1 632.03 -0.0203 3 0 11 12 E1 687.73 0.0228 3 2 12 11 A 553.40 -0.0251 3 0 12 13 E1 579.10 -0.0035 4 2 2 1 E1 635.06 -0.0166 3 0 12 11 E1 738.64 0.0339 4 2 2 3 E2 631.50 -0.0151 3 0 13 12 A 703.13 0.0404 4 2 3 2 A 664.55 -0.0154 3 1 9 8 E1 686.69 -0.0395 4 2 6 5 E1 634.39 -0.0183 3 1 9 10 E2 690.74 0.0315 4 2 7 6 A 661.74 -0.0169 3 1 10 9 E2 518.29 -0.0294 4 3 1 2 A 661.37 -0.0141 3 1 11 12 E1 502.48 -0.0451 4 3 4 3 E2 694.41 -0.0144 3 1 11 10 E1 559.86 -0.0228
Origins of new torsional subbands of CH3OH
113
120
121
111
502.48
687.73
125.14(Moruzzi et al.)
60.11 ~ 1.8 THz
THz Interstellar Lines are Predicted from FTIR Combination Differences
Kvt
Description obs / cm-1
A'1 OH stretch 3682
CH asym stretch 2999
CH sym stretch 2844
4 CH3 asym bend 1478
5 CH3 sym bend 1455
6 OH bend 1340
7 CH3 in-plane rock 1075
8 CO stretch 1034
A"9 CH asym stretch 2970
10 CH3 o-o-p bend 1465
11 CH3 o-o-p rock 1145
12 CH3 torsion 272
Vibrational modesof methanol
Wavenumbers from A. Serrallach, R. Meyer and Hs. H. Gunthard, J. Mol. Spectrosc. 52 (1974) 94-129.
Torsional combination bands
800 900 1000 1100 1200 1300 800 900 1000 1100 1200 1300
CLS FTIR Spectra of 13CH3OH and CD3OH
CD3OH
CO stretchOH bend
CD3 bend
CH3 in-plane rock
13CH3OH
CD3 in-plane rock
P(12)
P(13)
P(14)
P(17) P(16) P(15) P(14) P(13) P(12) P(11) P(10) P(9)
vt=1vt=0
Multiplet Structure in the O-18 CO-Stretch Band
(vt,K)=(1,-3)E
CH318OH CO-Stretch
900 1000 1100 1200 1300 1400 1500 1600 1700 900 1000 1100 1200 1300 1400 1500 1600 1700
CLS FTIR Spectrum of O-18 Methanol
CO Stretch Out-of-plane Rock
CH3 Bends
absb
vt = 1← 0 rivt = 0← 1 oh
"U" Subbands
1071.2 1071.4 1071.6 1071.8 1072.0 1072.2 1072.4 1072.6 1072.8 1073.0 1071.2 1071.4 1071.6 1071.8 1072.0 1072.2 1072.4 1072.6 1072.8 1073.0
In-plane Rock
3A
-8E
4A 7A-5E6E3E
1340.5 1341.0 1341.5 1342.0 1342.5 1340.5 1341.0 1341.5 1342.0 1342.5
OH Bend
7A3A7E8A
1317.5 1317.6 1317.7 1317.8 1317.9 1318.0 1318.1 1318.2 1318.3 1318.4 1318.5 1318.6 1318.7 1318.8 1318.9 1319.0 1317.5 1317.6 1317.7 1317.8 1317.9 1318.0 1318.1 1318.2 1318.3 1318.4 1318.5 1318.6 1318.7 1318.8 1318.9 1319.0
1319.0 1319.1 1319.2 1319.3 1319.4 1319.5 1319.6 1319.7 1319.8 1319.9 1320.0 1320.1 1320.2 1320.3 1320.4 1320.5 1319.0 1319.1 1319.2 1319.3 1319.4 1319.5 1319.6 1319.7 1319.8 1319.9 1320.0 1320.1 1320.2 1320.3 1320.4 1320.5
1320.5 1320.6 1320.7 1320.8 1320.9 1321.0 1321.1 1321.2 1321.3 1321.4 1321.5 1321.6 1321.7 1321.8 1321.9 1322.0 1320.5 1320.6 1320.7 1320.8 1320.9 1321.0 1321.1 1321.2 1321.3 1321.4 1321.5 1321.6 1321.7 1321.8 1321.9 1322.0
Loomis-Wood Plot for Line Series Identification
OH bend, vt = 0 OH bend, vt = 1In-plane rock, vt = 1-0 U0 subband
1100.0
1200.0
1300.0
1400.0
1500.0
1600.0
1700.0
1800.0
0 1 2 3 4 5 6 7 8 9 10 11 12
K-Reduced Torsion-Vibration Energy Map
K Value
K-R
educ
ed E
nerg
y (c
m-1)
Connect the Dots???
1100.0
1200.0
1300.0
1400.0
1500.0
1600.0
1700.0
1800.0
0 1 2 3 4 5 6 7 8 9 10
K Value
K-R
educ
ed E
nerg
y (c
m-1)
O-18 K-Reduced Torsion-Vibration Energy Map (sensitive to K = 0 anharmonic perturbations)
CO stretch, vt = 0
CO stretch, vt = 1
CO stretch, vt = 2
In-plane rock, vt = 0
In-plane rock, vt = 1
Out-of-plane rock, vt = 0
U0 substates
CH3 asym bend, vt = 0
OH bend, vt = 0
OH bend, vt = 1U1 substates
U2 substates
1400
1405
1410
1415
1420
1425
1430
0 5 10 15 20 25 30 35 40
( A,co,0,9)
( A,co,1,5)
( A,ri,1,1+)
( A,ri,1,1-)
( A,co,1,0)
( A,ri,0,8)
( A,co,1,3)
( A,ro,0,6)
Level-Crossing Resonances
J Value
J-R
educ
ed E
nerg
y (c
m-1)
CH3 o-o-p rock
CH3 in-plane rock
CO stretch
O-18 J-Reduced Rot-Tor-Vib Energy Map (sensitive to level-crossings and J-localized perturbations)
O-18 CO Stretch - R.M. Lees, Reba-Jean Murphy, Giovanni Moruzzi, Adriana Predoi-Cross, Li-Hong Xu, D.R.T. Appadoo, B. Billinghurst, R.R.J. Goulding and Saibei Zhao, J. Mol. Spectrosc. 256, 91-98 (2009).
Summary
New highly excited torsional subbands have been assigned in the FIR
spectrum of normal CH3OH locating 6 new substates for vt = 2, 9 for vt = 3,
and 5 for vt = 4 at high K-values, providing predictions for potential THz
astronomical lines from combination differences and important new torsional constraints for future global fitting of the ground vibrational dataset.
Vibrational bands have been recorded for the CO-stretching, CH3-rocking,
OH-bending and CH3-bending modes of 13CH3OH, CH318OH and CD3OH.
The K- and J-reduced energy plots of CH318OH show complex mixtures of
fundamental and torsional combination states with torsion-mediated intermode interactions that perturb the regular subband patterns, plus U substates of as yet unconfirmed vibrational parentage.
Isotopic shifts in subband origins and B-values suggest the U states are
torsion-rocking combination states, possibly mixed with the OH-bend.